From ad3c6713da811659c2137460d09d0149192be7aa Mon Sep 17 00:00:00 2001
From: Frederic Junod <frederic.junod@camptocamp.com>
Date: Wed, 9 Dec 2015 13:30:54 +0100
Subject: [PATCH 1/2] Return if the element is added to the
 ol.structs.PriorityQueue

---
 src/ol/structs/priorityqueue.js            |  3 +++
 test/spec/ol/structs/priorityqueue.test.js | 13 ++++++++++++-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/ol/structs/priorityqueue.js b/src/ol/structs/priorityqueue.js
index e943796e34..a1ab4c946e 100644
--- a/src/ol/structs/priorityqueue.js
+++ b/src/ol/structs/priorityqueue.js
@@ -122,6 +122,7 @@ ol.structs.PriorityQueue.prototype.dequeue = function() {
 /**
  * Enqueue an element. O(log N).
  * @param {T} element Element.
+ * @return {boolean} The element was added to the queue.
  */
 ol.structs.PriorityQueue.prototype.enqueue = function(element) {
   goog.asserts.assert(!(this.keyFunction_(element) in this.queuedElements_),
@@ -132,7 +133,9 @@ ol.structs.PriorityQueue.prototype.enqueue = function(element) {
     this.priorities_.push(priority);
     this.queuedElements_[this.keyFunction_(element)] = true;
     this.siftDown_(0, this.elements_.length - 1);
+    return true;
   }
+  return false;
 };
 
 
diff --git a/test/spec/ol/structs/priorityqueue.test.js b/test/spec/ol/structs/priorityqueue.test.js
index bacf751ad6..1c9aded427 100644
--- a/test/spec/ol/structs/priorityqueue.test.js
+++ b/test/spec/ol/structs/priorityqueue.test.js
@@ -28,14 +28,25 @@ describe('ol.structs.PriorityQueue', function() {
     });
 
     it('enqueue adds an element', function() {
-      pq.enqueue(0);
+      var added = pq.enqueue(0);
       expect(function() {
         pq.assertValid();
       }).not.to.throwException();
+      expect(added).to.be(true);
       expect(pq.elements_).to.eql([0]);
       expect(pq.priorities_).to.eql([0]);
     });
 
+    it('do not enqueue element with DROP priority', function() {
+      var added = pq.enqueue(Infinity);
+      expect(function() {
+        pq.assertValid();
+      }).not.to.throwException();
+      expect(added).to.be(false);
+      expect(pq.elements_).to.eql([]);
+      expect(pq.priorities_).to.eql([]);
+    });
+
     it('maintains the pq property while elements are enqueued', function() {
       var i;
       for (i = 0; i < 32; ++i) {

From 7192644c07c1bb40269ac6453c04da65ec0b937e Mon Sep 17 00:00:00 2001
From: Frederic Junod <frederic.junod@camptocamp.com>
Date: Wed, 9 Dec 2015 13:38:09 +0100
Subject: [PATCH 2/2] Register the change callback when the tile is enqueued

---
 src/ol/tilequeue.js | 29 ++++++++++++++++++++++++++---
 1 file changed, 26 insertions(+), 3 deletions(-)

diff --git a/src/ol/tilequeue.js b/src/ol/tilequeue.js
index 43a588a1aa..02e9221116 100644
--- a/src/ol/tilequeue.js
+++ b/src/ol/tilequeue.js
@@ -55,10 +55,30 @@ ol.TileQueue = function(tilePriorityFunction, tileChangeCallback) {
    */
   this.tilesLoading_ = 0;
 
+  /**
+   * @private
+   * @type {Object.<string,boolean>}
+   */
+  this.tilesLoadingKeys_ = {};
+
 };
 goog.inherits(ol.TileQueue, ol.structs.PriorityQueue);
 
 
+/**
+ * @inheritDoc
+ */
+ol.TileQueue.prototype.enqueue = function(element) {
+  var added = goog.base(this, 'enqueue', element);
+  if (added) {
+    var tile = element[0];
+    goog.events.listen(tile, goog.events.EventType.CHANGE,
+        this.handleTileChange, false, this);
+  }
+  return added;
+};
+
+
 /**
  * @return {number} Number of tiles loading.
  */
@@ -78,7 +98,11 @@ ol.TileQueue.prototype.handleTileChange = function(event) {
       state === ol.TileState.EMPTY) {
     goog.events.unlisten(tile, goog.events.EventType.CHANGE,
         this.handleTileChange, false, this);
-    --this.tilesLoading_;
+    var tileKey = tile.getKey();
+    if (tileKey in this.tilesLoadingKeys_) {
+      delete this.tilesLoadingKeys_[tileKey];
+      --this.tilesLoading_;
+    }
     this.tileChangeCallback_();
   }
 };
@@ -95,9 +119,8 @@ ol.TileQueue.prototype.loadMoreTiles = function(maxTotalLoading, maxNewLoads) {
          this.getCount() > 0) {
     tile = /** @type {ol.Tile} */ (this.dequeue()[0]);
     if (tile.getState() === ol.TileState.IDLE) {
-      goog.events.listen(tile, goog.events.EventType.CHANGE,
-          this.handleTileChange, false, this);
       tile.load();
+      this.tilesLoadingKeys_[tile.getKey()] = true;
       ++this.tilesLoading_;
       ++newLoads;
     }